SUPPLEMENTAL REPORT—HANGING ROCK DISTRICT. 893 
counties; but inasmuch as the Zoar or Blue Limestone, which is also 
found in this district, is equally with the Gray Limestone, ferriferous, 
this designation will be replaced here by a geographical name. As this 
limestone is everywhere developed and everywhere known throughout 
the Hanging Rock District, and is almost the sole reliance of all the 
southern furnaces for flux, it will be styled the Hanging Rock Limestone. 
It is ordinarily known as the Gray Limestone. It is the duplicate of the 
Gray Limestone of the eastern counties. This last seam, it will be re- © 
membered, received from Prof. Andrews the name of Putnam Hill Lime- 
stone, from a fine exposure opposite Zanesville. As the Putnam Hill 
Limestone is followed westward, it is found to grow thin and finally dis- 
appear. It is in good force as a flint and lime horizon at New Lexington, 
Perry county—being shown in a section of five feet in the railroad cut, 
just east of the station, but if cannot be followed, without change, far 
beyond this point. It seems to become an ore horizon to the southward. 
The “ Limestone Kidney” ore of the southern counties lies very near its 
proper place. A bastard limestone is found associated with this ore seam 
at McCuneville and elsewhere. But just as the Putnam Hill Lime- 
stone fails,a new one makes its appearance. In the neighborhood of 
Bristol, Perry county, a horizon of lime, flint, and ore appears from fif- 
teen to thirty feet above the Putnam Hill Limestone. Its usual distance 
ig a little more than twenty feet. It, too, is a gray limestone, and it takes 
its place in a series of fifty or sixty feet of strata that repeat, in a remark- 
able way, the order of the strata found with the Putnam Hill Limestone. 
It will be remembered that the Zoar or Blue Limestone very often occurs 
in the district in two courses, from fourteen to twenty-two feet apart. 
As this interval is sometimes wholly filled with fossiliferous, calcareous 
shales, and as the limestones indicate the same conditions of growth, 
there can be no question as to their both belonging to the same epoch; 
and they are, therefore, distinguished as the Upper and Lower Zoar 
Limestones. It will be hereafter shown that the Cambridge Limestone 
is split in the same way, its two courses being separated by intervals 
varying from one to twenty-seven feet, and the separate courses being | 
known as Upper and Lower Cambridge. There is almost equal warrant 
for counting these two gray limestones as belonging to one epoch, and 
giving them the same general name. The difference between the cases 
does not lie in the magnitude so much as in the character of the inter- 
vals. The Putnam Hill and Hanging Rock horizons are separated in 
the northern part of the field by sandstones which indicate a more com- 
plete break than is shown by the fire-clays and fossiliferous shales re- 
ferred to above. The Hanging Rock Limestone will accordingly be 
treated by itself in the following review. 
